DE102008010555A1 - Method for controlling internal-combustion engine operated with e.g. gasoline/ethanol fuel mixture, involves obtaining coefficient pair from protic fuel coefficient and oxygen demand coefficient and deducing control parameters for engine - Google Patents

Abstract

The method involves determining a protic fuel coefficient (30) from a signal of a fuel sensor i.e. capacitive sensor (20), where the fuel sensor is provided in an internal-combustion engine. An oxygen demand coefficient is determined from the air amount supplied to the internal combustion engine, the supplied fuel amount and the signal of an exhaust gas probe (22). Coefficient pair is obtained from the protic fuel coefficient and the oxygen demand coefficient. The control parameters for internal combustion engine are deduced from the coefficient pair.

Description

State of the art

The The invention relates to a method for controlling an internal combustion engine, wherein the internal combustion engine with a first fuel and a second fuel or with a fuel mixture of a first and at least a second fuel is operated, wherein the Internal combustion engine, a fuel sensor for determining fuel properties, a fuel metering device, a device for determination the amount of air supplied and at least one exhaust gas probe having in an exhaust passage.

Internal combustion engines On the basis of gasoline engines are generally fueled Hydrocarbons derived from fossil fuels based on refined Operated oil. To this fuel is increasingly off renewable raw materials (plants) produced alcohol, for example Ethanol or methanol, in different mixing ratios added. In the US and Europe is often a mix of 75-85% Ethanol and 15-25% gasoline used under the brand name E85. The internal combustion engines are designed so that they are both pure Gasoline can also be operated with mixtures up to E85; There are also known concepts according to which the internal combustion engine is operable to hydrous E100. This is called "flex-fuel operation" designated. For economical operation with low pollutant emissions At the same time high engine power must be the operating parameters in flex-fuel operation to the respective existing fuel mixture be adjusted. By way of example, there is a stoichiometric air / fuel ratio at 14.7 parts by weight of air per part of gasoline before use ethanol, however, requires an air content of 9 parts by weight become. Furthermore, fuel mixtures differ different Composition clearly in their ignition behavior.

about The interaction of sensors becomes the instantaneous fuel composition before the injection time and the instantaneous exhaust gas composition, So the oxygen partial pressure in the exhaust gas, determined and to the control electronics the internal combustion engine passed on. Based on the thus determined Composition of the fuel mixture will burn the Internal combustion engine, in particular via the setting of most favorable air / fuel ratio, optimized.

to Determining the composition of the fuel mixture will be different Fuel type sensors, also called "fuel composition sensors" designated used. Fuel type sensors use the different ones Properties of alcohol and gasoline for determination of fuel composition. For example, ethanol is a protic solvent, which contains hydrogen ions and a large, however, dependent on the water content, dielectric constant having. Gasoline, on the other hand, is an aprotic solvent with a small dielectric constant. Based on that There are fuel type sensors which determine the fuel composition determine the dielectric properties of the fuel mixture. Other fuel type sensors use the different electrical Conductivity, the different heat capacity or the different optical properties of the fuels, for example the different refractive indices.

In the DE 41 12 574 For example, a fuel supply system for an internal combustion engine is described in which the operating state of the internal combustion engine is detected and the amount of fuel to be supplied is controlled in accordance with the result of this detection. Here, it is provided that the fuel supply system includes a fuel type detecting means for detecting the fuel type and a calculating means for calculating a fuel type corresponding theoretical air-fuel ratio in accordance with the detection result of the fuel-type detection means and the amount of fuel to be supplied using the controlled by the computing means theoretical air-fuel ratio is controlled as the target air-fuel ratio. In this case, it can be provided that the fuel-type detection means detects the fuel type by measuring at least one of the refractive index, the dielectric constant or the molar heat of the fuel in the liquid state.

adversely Here is that the dielectric constant and the electrical conductivity of the fuel strongly by protic Admixtures is influenced. For example, an over the capacity or conductivity of the fuel mixture determined ethanol content by the high water sensitivity of Measurement must be strongly faulty. Furthermore, additives in gasoline, for example, used as a knocking agent Methyl tert-butyl ether (MTBE) or higher alcohols, one make it difficult to quantitatively determine, for example, an ethanol content.

The determination of the composition of the fuel mixture based on the refractive index or The heat capacity is hardly used today for cost and robustness reasons.

It It is an object of the invention to provide a method which a reliable adjustment of the operating parameters of a Internal combustion engine when using fuel mixtures of at least allows two fuels.

Advantages of the invention

The The object of the invention is achieved in that from a Signal of the fuel sensor determines a protic fuel coefficient is and that supplied from the internal combustion engine Air volume, the amount of fuel supplied and the signal the exhaust gas probe an oxygen demand coefficient is determined and that from the protic fuel coefficient and the oxygen demand coefficient Coefficient pairs are formed and that of the pairs of coefficients control parameters are derived for the internal combustion engine.

Of the protic coefficient is dependent on those in the fuel / fuel mixture existing portions of functional groups that make up hydrogen ions split off as protons, so they can be dissociated. So water is a Brönsted acid and can be used in Protons and hydrodroxyl ions dissociate and strong hydrogen bonds form. Alcohols such as methanol and ethanol also show the tendency for hydrogen bonding and an im Compared to hydrocarbons high degree of dissociation, however less than that of the water.

ever higher the proportion of polar and protic hydroxyl groups in the fuel / fuel mixture, the higher is conditional by hydrogen bonding, its enthalpy of vaporization. Since the evaporation behavior of the fuel / fuel mixture significantly influences its ignition properties, the protic coefficient is primarily used for the setting of Ignition parameters and the retrieval of possible Additional measures for starting the engine, such as metering of secondary fuel or fuel preheating. Next the information on the evaporation behavior complements the protic fuel coefficient Information on calorific value and air requirement of the fuel / fuel mixture.

Of the Oxygen demand coefficient primarily describes the air requirement and the most favorable air / fuel ratio, But also lets conclusions on the Calorific value of the fuel / fuel mixture used.

There the coefficients complement each other in their information content or partially overlap, can be through Forming corresponding coefficient pairs the most important properties and the burning behavior of a fuel / fuel mixture the protic fuel coefficient and the oxygen demand coefficient clearly classify. A detailed analysis of the fuel composition, for example, the determination of the ethanol content of a gasoline / ethanol fuel mixture, eliminated. Since the information of the two coefficients complement or partially overlap, may be the basis of the formation of the coefficients Measurements may be buggy, resulting in low cost sensors allows.

Corresponding a particularly preferred embodiment variants of the method it can be provided that from the signal of the exhaust gas probe Carbon-to-hydrogen ratio of the fuel or fuel mixture is determined and that from the protic Fuel coefficient, the oxygen demand coefficient and the carbon-hydrogen ratio coefficient Beverage triplets are formed and that from the triplers control parameters are derived for the internal combustion engine.

Of the Carbon-to-Hydrogen Ratio includes information about the carbon to hydrogen ratio in the fuel / fuel mixture and lets you draw conclusions about its calorific value and burning behavior too. Due to the faster compared to carbon and complete oxidation of hydrogen shares can fuels / fuel mixtures with similar oxygen demand, but different carbon-to-hydrogen ratio, differ in their reaction kinetics and reaction enthalpy. The carbon-hydrogen ratio added Thus, the information of the protic fuel coefficient and the Oxygen Demand-adjustment factor.

It can preferably be provided that the protic fuel coefficient is determined via a measurement of the dielectric constant of the fuel or of the fuel mixture. The determination of the dielectric constants of fuel / fuel mixtures with corresponding fuel type sensors, for example for determining the composition of a fuel mixture of gasoline and ethanol, is known. However, exactly metering and correspondingly expensive fuel type sensors are to be provided in order to to allow the needed accurate determination of the composition of the fuel mixture. By forming the coefficient pairs or the coefficient triplets, the accuracy of the specific dielectric constant of the fuel / fuel mixture can be lower, which enables the use of cost-effective fuel type sensors.

As can be seen from the following table, the dielectric constant and thus the protic fuel coefficient correlate with significant fuel properties. Thus, gas has a dielectric constant of 2 and a heat of evaporation of 440 kJ / kg. Ethanol E100 and methanol show similar heat of vaporization (910 kJ / kg and 850 kJ / kg, respectively) for similar dielectric constants (25 and 30, respectively), while water has a heat of vaporization of 2250 kJ / kg at a dielectric constant of 88. A fuel mixture of 85% ethanol and 15% gasoline (E85) with a dielectric constant of 21 has a heat of evaporation of 840 kJ / kg. Fuel component Normal petrol E85 E100 methanol water permittivity 2 21 25 35 88 Heat of evaporation [kJ / kg] 440 840 910 850 2250 Oxygen content [wt.%] <2.8 29.8 34.7 49.9 89.5 Calculated O ₂ requirement per kg of fuel [kg] 8.0 3.0 2.0 1.5 n / A Air / fuel ratio 14.6 10.0 8.9 6.4 n / A Calorific value / gallon [BTU] 120000 85000 80000 60000 n / A Ignition temperature [° C] > 220 about 400 420 450 n / A

This correlation makes it possible to deduce from the determined dielectric constant the heat of vaporization and thus, for example, the ignition properties of the fuel / fuel mixture, without the exact knowledge of the composition of the fuel / fuel mixture. A resolution of the contributions of H ₂ O, CH ₃ OH and C ₂ H ₅ OH and thus a determination of the composition of the fuel mixture is not necessary.

As the table further shows correlates the relative permittivity with the calorific value and with the air / fuel ratio or the calculated oxygen demand, so that from the Dielectric constant or the resulting protic fuel coefficient also conclusions on the calorific value and the air requirement of the fuel / fuel mixture can be pulled.

Corresponding A preferred embodiment of the invention may be provided that the oxygen demand coefficient at stable Operating conditions of the internal combustion engine by regulation the stoichiometric lambda value from the lambda control is determined. Here are the required amount of air and fuel known exactly. The oxygen demand coefficient determines the setting an exhaust and consumption-optimized engine continuous operation under Consideration of exhaust gas recirculation.

is it provided that the carbon-to-hydrogen ratio coefficient is determined by using as exhaust gas a broadband lambda probe and that the exhaust gas probe at least temporarily unburned or partially combusted fuel or unburned or partially burned Fuel mixture is supplied and that from the curvature the characteristic of the exhaust gas probe in the fat region of the carbon-hydrogen ratio coefficient as a relative molecular carbon to hydrogen ratio is determined, so the fuel or the fuel mixture over a value triplets are described. The unburned fuel or the unburned fuel mixture can by a temporarily strongly enriched operating condition of the internal combustion engine or by injecting fuel / fuel mixture or by a test injection during a pushing operation to the broadband lambda probe installed as near as possible to the engine reach.

According to an alternative embodiment variant of the invention, it can be provided that the carbon-hydrogen ratio coefficient is determined by using a broadband lambda probe as the exhaust gas probe and that the exhaust gas probe is at least temporarily supplied with unburned or partially combusted fuel or unburned or partially combusted fuel mixture, that about the set temperature of preferably 650 ° C, the exhaust gas probe periodically allows complete oxidation of the hydrogen and a partial oxidation of the carbon in the measuring chamber of the exhaust gas probe, and is adjusted to a high temperature of preferably 850 ° C and that the carbon-to-hydrogen ratio is determined from the difference in pumping current at high temperature and at low temperature. Again, the unburned fuel or the unburned fuel mixture by a temporarily greatly enriched operating condition of the engine or by Nacheinspritzen fuel / fuel mixture or by a test injection during a push operation to get the most close to the engine installed wide-band lambda probe.

Corresponding a further alternative embodiment of the method it may be provided that the carbon-hydrogen ratio coefficient is determined by using as exhaust gas probe one for hydrocarbons sensitive exhaust gas probe is used and that the exhaust gas probe at least temporarily unburned or partially combusted fuel or unburnt or partially combusted fuel mixture is supplied. In this case, the outer electrode of an example stoichiometric Lambda probe made of a Pt / Au alloy, the carbon-hydrogen shares detected, with such lambda probes compared to the cross-sensitivity Exploit fat gas components. The really big measurement uncertainty in the determination of the carbon-hydrogen content with such Flue gas probes are corrected by the formation of the triplets.

The Coefficient pairs or coefficient triplets allow control of internal combustion engines, which with fuel mixtures of different Composition can be operated. For controlling the internal combustion engine, it may therefore be provided that from the Coefficient pairs or the triplate the control parameters for the engine start and / or the exhaust and consumption optimized operation the internal combustion engine can be determined. Thereby can For example, the amount of fuel supplied, the ignition, the fuel preheating the control position and the exhaust gas recirculation to be controlled.

Farther It may be provided that using the coefficient pairs or the triplicate fuel-specific consumption data determined become. For example, an ethanol consumption and a fuel consumption in internal combustion engines, which with mixtures operated from ethanol and gasoline, determined separately and for example the operator of the internal combustion engine are displayed.

The Method can preferably be used to control an internal combustion engine use which with a gasoline / ethanol fuel mixture and / or a gasoline / methanol fuel mixture and / or a gasoline / ethanol / methanol fuel mixture is operated.

Brief description of the drawings

The Invention will be described below with reference to the FIG Embodiment explained in more detail. Show it:

1 in a schematic representation of a flowchart for controlling an internal combustion engine. Embodiments of the invention

1 shows a schematic diagram of a flowchart for controlling an internal combustion engine.

A control unit 10 for controlling the internal combustion engine, not shown, are a capacitive sensor 20 , a lambda control 21 and an exhaust gas probe 22 assigned. The exhaust gas probe 22 can be used as a broadband lambda probe 22.1 or as a jump probe with HC functionality 22.2 be executed.

The capacitive sensor supplies as output a protic fuel coefficient 30 to the control unit 10 , The lambda control 21 puts the control unit 10 an oxygen demand coefficient 31 available while the exhaust probe 22 the control unit 10 a carbon-to-hydrogen ratio 32 provides.

The process in the control unit 10 is schematically in a first stage 11 and a second stage 12 divided up. Starting from the second stage 12 the ignition / engine start setting is made 40 , setting optimal engine operation 41 , the setting exhaust gas recirculation 42 as well as the expenditure consumption statistics 43 ,

The protic fuel coefficient 30 is used as the sum signal of a measurement of Dielelektrizitätskons a fuel or a fuel mixture with the aid of the capacitive sensor 20 won. The larger the proportion of polar and protic hydroxyl groups (HOH, CH ₃ -OH, C ₂ H ₅ -OH,...) In the fuel / fuel mixture, the greater is its enthalpy of vaporization due to hydrogen bonding. Since the evaporation behavior of the fuel / fuel mixture significantly influences its ignition properties, the protic fuel coefficient is used 30 especially for setting ignition parameters and retrieving possible additional measures for the start of the internal combustion engine, such as the addition of secondary fuel or the fuel preheating.

Here, the correlation between the fuel properties and the dielectric constant is used. Water changes the fuel properties, such as the heat of vaporization, very strong, but also has a very large influence on the dielectric constant. Methanol and ethanol also show a marked, but already graded, lower influence on the dielectric constant at average heat of vaporization. Gasoline, on the other hand, has a very low dielectric constant and shows the lowest heat of vaporization. Based on the protic fuel coefficient 30 Accordingly, without precise knowledge of the composition of the present fuel mixture, it describes its vaporization and ignition behavior. In addition, the protic fuel coefficient provides 30 Information on calorific value and air requirement of the fuel / fuel mixture.

The oxygen demand coefficient 31 is from the lambda control 21 obtained at stable operating conditions of the internal combustion engine by adjusting to the stoichiometric lambda value at a known amount of air and fuel. The oxygen demand coefficient 31 Determines the setting of an exhaust and consumption optimized engine continuous operation taking into account the exhaust gas recirculation.

In many cases, classification of a fuel / fuel mixture by the protic fuel coefficient is sufficient 30 and the oxygen demand coefficient 31 for controlling an internal combustion engine. It should be noted that fuel mixtures with different hydrogen, carbon and oxygen contents in the molecule in total an identical oxygen demand coefficient 31 can have. Furthermore, it should be noted that the possible water content, for example in ethanol-gasoline fuel mixtures, increases sharply with increasing ethanol content. Thus, at 25 ° C, fuel E10, ie a mixture of 10% ethanol and 90% gasoline, forms a miscibility gap as low as 0.5% water. With E30, there is a miscibility gap from about 2.0% of water, with E85 there is no miscibility gap, so theoretically up to 15% of water can be contained without segregation. For fuel mixtures of methanol and gasoline, the conditions are similar. For this reason, the protic fuel coefficient run 30 and the oxygen demand coefficient 31 with very high gasoline content very close together. A large variance of the fuel properties and thus the coefficients occurs only at high alcohol content by large fluctuations in the gasoline and water content.

In addition to the protic fuel coefficient 30 and the oxygen demand coefficient 31 another factor may be included for classification of the fuel / fuel mixture. This carbon-hydrogen ratio 32 supplements the characterization of the fuel / fuel mixture, for example, by information on the relative molecular hydrogen-carbon ratio. Due to the faster and more complete oxidation of hydrogen fractions compared to carbon, fuels with the same oxygen demand, but different carbon-hydrogen ratio, can differ in their reaction kinetics and in their reaction enthalpy, which is due to the carbon-hydrogen ratio 32 is taken into account.

The carbon-hydrogen ratio 32 can also be obtained from the lambda control, but in a temporarily greatly enriched operating condition of the internal combustion engine or by post-injection of fuel / fuel mixture or by a test injection during a coasting operation. Prerequisite is in any case the transport of unburned or partially combusted fuel / fuel mixture to the exhaust gas probe arranged in front of a first catalyst 22 ,

According to a first embodiment for determining the carbon-hydrogen ratio coefficient 32 is the exhaust gas probe 22 as a broadband lambda probe 22.1 executed with a pumping and a Nernst cell, which is kept in controlled operation at a constant temperature. The Nernst voltage is regulated to 450 mV, which corresponds to a stoichiometric operation of the internal combustion engine. Equal amounts of gas occupy the same volume at the same temperature and pressure. In the reaction of hydrogen, one molecule of water per molecule is introduced into the measuring chamber of the broadband lambda probe 22.1 pumped oxygen ion free, with carbon only half a molecule. Therefore, the reaction of hydrogen produces a larger volume of gas than the reaction of the carbon. A carbon-hydrogen molecule is thus clearly identified by the number of molecules formed. A number h of each fed sow The resulting molecules therefore indicate the carbon-hydrogen ratio. For pure carbon C h = 0.5; with pure hydrogen H ₂ h = 1.0. For C ₈ H ₁₈ h = 0.68 and for C ₂ H ₅ OH h = 0.83. This resulting gas volume leads with higher carbon-to-hydrogen ratio in the exhaust gas of the internal combustion engine to an increase in pressure in the measuring chamber and a curvature of the characteristic curve in the fats upwards. From the pressure increase or the curvature of the characteristic per oxygen pumped in, it is concluded that the hydrogen content of the reacting gases and the carbon-hydrogen ratio 32 educated.

According to a second embodiment for determining the carbon-hydrogen ratio coefficient 32 is the exhaust gas probe 22 again as a broadband lambda probe 22.1 executed, which unburned or partially combusted fuel or unburned or partially burned fuel mixture is supplied. In this case, the temperature is lowered periodically in such a way that, although the oxidation of the hydrogen is still complete, the carbon is only partially oxidized, for example to carbon monoxide. From the pumping current, which is absent for complete oxidation of the carbon at normal temperature, the carbon-hydrogen ratio can be determined quantitatively, from which the carbon-hydrogen ratio is calculated 32 is determined.

For a third embodiment for determining the carbon-hydrogen ratio 32 becomes a crack probe with HC functionality 22.2 used. The jumping probe with HC functionality 22.2 has an outer electrode made of a Pt / Au alloy. Such probes deliver a voltage signal in the lean, which is used to determine the lambda value. In addition, they show a useful cross-sensitivity for fatty gas fractions. Here too, it is advantageous that the requirements with regard to the measurement accuracy and the signal resolution can be substantially lower than with a stand-alone probe since the signal information is supplemented and corrected by combining with the other coefficients.

In a control of the internal combustion engine based on the protic fuel coefficient 30 and the oxygen demand coefficient 31 forms the control unit 10 in the first stage 11 from the protic fuel coefficient 30 and the oxygen demand coefficient 31 a value pair. In addition, the carbon-hydrogen ratio increases 32 involved, so forms the first stage 11 the control a corresponding triplate.

Out of the first stage 11 converted and summarized numerical coefficient pairs or coefficient triplets is in the second stage 12 , For example, via a comparison of the numerical coefficient pairs or coefficient triplets with stored values in a map, the data set for the adjustment of the operation of the internal combustion engine carried out. These are in the form of the setting ignition / engine start 40 for example, the amount of fuel, the ignition timing or the fuel preheating specified. The settings for the exhaust and consumption-optimized operation of the internal combustion engine are optimized by setting the engine 41 and adjustment exhaust gas recirculation 42 specified. Fuel-specific consumption statistics, for example on ethanol consumption or gasoline consumption, are determined by the variety-specific consumption statistics 43 output.

Because the information of the protic fuel coefficient 30 , the oxygen demand coefficient 31 and possibly the carbon-hydrogen ratio 32 supplement or partially overlap the properties of the fuel / fuel mixture, the properties and the burning behavior of example any flex-fuel mixtures can be clearly described by the pairs of coefficients formed or triplets. The fuel or the fuel mixture is classified by the measured coefficients, a detailed analysis of the fuel composition, for example, an ethanol content in an ethanol-gasoline fuel mixture omitted. It is advantageous that the input variables obtained by the individual sensors may be heavily faulty, which leads to low sensor costs.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• - DE 4112574 [0005]

Claims (10)

Method for controlling an internal combustion engine, wherein the internal combustion engine with a first fuel and a second fuel or with a fuel mixture of a first and at least a second fuel is operated, the internal combustion engine, a fuel sensor for determining fuel properties, a fuel metering device, a device for Determining the amount of air supplied and at least one exhaust gas probe in an exhaust passage, characterized in that from a signal of the fuel sensor, a protic fuel coefficient ( 30 ) is determined and that from the internal combustion engine supplied air quantity, the amount of fuel supplied and the signal of the exhaust gas probe an oxygen demand coefficient ( 31 ) and that from the protic fuel coefficient ( 30 ) and the oxygen demand coefficient ( 31 ) Pairs of coefficients are formed and that control parameters for the internal combustion engine are derived from the pairs of coefficients. A method according to claim 1, characterized in that from the signal of the exhaust gas probe 22 a carbon-to-hydrogen ratio ( 32 ) of the fuel or fuel mixture and that from the protic fuel coefficient ( 30 ), the oxygen demand coefficient ( 31 ) and the carbon-to-hydrogen ratio ( 32 ) Triplets are formed and that derived from the triplets control parameters for the internal combustion engine. Method according to claim 1 or 2, characterized in that the protic fuel coefficient ( 30 ) is determined via a measurement of the dielectric constant of the fuel or of the fuel mixture. Method according to one of claims 1 to 3, characterized in that the oxygen demand coefficient ( 32 ) at stable operating states of the internal combustion engine by adjusting to the stoichiometric lambda value from the lambda control ( 21 ) is determined. Method according to one of claims 1 to 4, characterized in that the carbon-hydrogen ratio ( 32 ) is determined by as the exhaust gas probe 22 a broadband lambda probe ( 22.1 ) is used and that the exhaust gas probe 22 at least temporarily unburned or partially combusted fuel or unburned or partially combusted fuel mixture is supplied and that from the curvature of the characteristic of the exhaust gas probe 22 in the fat region of the carbon-hydrogen ratio coefficient ( 32 ) is determined as a relative molecular carbon to hydrogen ratio. Method according to one of claims 1 to 4, characterized in that the carbon-hydrogen ratio ( 32 ) is determined by as the exhaust gas probe 22 a broadband lambda probe ( 22.1 ) is used and that the exhaust gas probe 22 at least temporarily unburned or partially burned fuel or unburned or partially burned fuel mixture is supplied to the set temperature over the exhaust gas probe 22 periodically a complete oxidation of the hydrogen and a partial oxidation of the carbon in the measuring chamber of the exhaust gas probe 22 is controlled and controlled to a high temperature and that the carbon-to-hydrogen ratio ( 32 ) is determined from the difference in pumping current at high temperature and at low temperature. Method according to one of claims 1 to 4, characterized in that the carbon-hydrogen ratio ( 32 ) is determined by using as exhaust gas probe ( 22 ) an exhaust gas probe sensitive to hydrocarbons ( 22 ) and that the exhaust gas probe ( 22 ) at least temporarily unburned or partially burned fuel or unburned or partially burned fuel mixture is supplied. Method according to one of claims 1 to 7, characterized in that from the coefficient pairs or the coefficient triplets the control parameters for the engine start and / or the exhaust gas and consumption optimized operation of the internal combustion engine be determined. Method according to one of claims 1 to 8, characterized in that using the coefficient pairs or the triplicate fuel-specific consumption data determined become. Application of the method according to one of the claims 1 to 9 for controlling an internal combustion engine, which with a Gasoline / ethanol fuel mixture and / or a gasoline / methanol fuel mixture and / or a gasoline / ethanol / methanol fuel mixture is operated.